X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDefaults.lhs;h=6c9de36a3c099979b3336f97596373b9c94847b7;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=66e56ef74509969aefa734a3b1fada9ea1ec2a62;hpb=d069cec2bd92d4156aeab80f7eb1f222a82e4103;p=ghc-hetmet.git

diff --git a/ghc/compiler/typecheck/TcDefaults.lhs b/ghc/compiler/typecheck/TcDefaults.lhs
index 66e56ef..6c9de36 100644
--- a/ghc/compiler/typecheck/TcDefaults.lhs
+++ b/ghc/compiler/typecheck/TcDefaults.lhs
@@ -4,77 +4,76 @@
 \section[TcDefaults]{Typechecking \tr{default} declarations}
 
 \begin{code}
-module TcDefaults ( tcDefaults, defaultDefaultTys ) where
+module TcDefaults ( tcDefaults ) where
 
 #include "HsVersions.h"
 
-import HsSyn		( HsDecl(..), DefaultDecl(..) )
-import RnHsSyn		( RenamedHsDecl )
-
-import TcMonad
-import TcEnv		( tcLookupGlobal_maybe )
-import TcMonoType	( tcHsType )
-import TcSimplify	( tcSimplifyCheckThetas )
-
-import TysWiredIn	( integerTy, doubleTy )
-import TcType           ( Type, mkClassPred )
+import HsSyn		( DefaultDecl(..), LDefaultDecl )
+import Name		( Name )
+import TcRnMonad
+import TcEnv		( tcLookupClass )
+import TcHsType		( tcHsSigType, UserTypeCtxt( DefaultDeclCtxt ) )
+import TcSimplify	( tcSimplifyDefault )
+import TcType           ( Type, mkClassPred, isTauTy )
 import PrelNames	( numClassName )
+import SrcLoc		( Located(..) )
 import Outputable
-import HscTypes		( TyThing(..) )
 \end{code}
 
 \begin{code}
-defaultDefaultTys = [integerTy, doubleTy]
-
-tcDefaults :: [RenamedHsDecl]
-	   -> TcM [Type] 	    -- defaulting types to heave
+tcDefaults :: [LDefaultDecl Name]
+	   -> TcM (Maybe [Type])    -- Defaulting types to heave
 				    -- into Tc monad for later use
 				    -- in Disambig.
-tcDefaults decls = tc_defaults [default_decl | DefD default_decl <- decls]
-
-tc_defaults [] = returnTc defaultDefaultTys
-
-tc_defaults [DefaultDecl [] locn]
-  = returnTc []		-- no defaults
 
-tc_defaults [DefaultDecl mono_tys locn]
-  = tcLookupGlobal_maybe numClassName	`thenNF_Tc` \ maybe_num ->
-    case maybe_num of
-	Just (AClass num_class) -> common_case num_class
-	other	          	-> returnTc []
-		-- In the Nothing case, Num has not been sucked in, so the 
-		-- defaults will never be used; so simply discard the default decl.
-		-- This slightly benefits modules that don't use any
-		-- numeric stuff at all, by avoid the necessity of
-		-- always sucking in Num
-  where
-    common_case num_class
-      = tcAddSrcLoc locn $
-    	mapTc tcHsType mono_tys	`thenTc` \ tau_tys ->
+tcDefaults [] 
+  = getDefaultTys		-- No default declaration, so get the
+				-- default types from the envt; 
+				-- i.e. use the curent ones
+				-- (the caller will put them back there)
+	-- It's important not to return defaultDefaultTys here (which
+	-- we used to do) because in a TH program, tcDefaults [] is called
+	-- repeatedly, once for each group of declarations between top-level
+	-- splices.  We don't want to carefully set the default types in
+	-- one group, only for the next group to ignore them and install
+	-- defaultDefaultTys
+
+tcDefaults [L locn (DefaultDecl [])]
+  = returnM (Just [])		-- Default declaration specifying no types
+
+tcDefaults [L locn (DefaultDecl mono_tys)]
+  = setSrcSpan locn 			$
+    addErrCtxt defaultDeclCtxt		$
+    tcLookupClass numClassName		`thenM` \ num_class ->
+    mappM tc_default_ty mono_tys	`thenM` \ tau_tys ->
     
- 		-- Check that all the types are instances of Num
- 		-- We only care about whether it worked or not
-    	tcAddErrCtxt defaultDeclCtxt		$
-    	tcSimplifyCheckThetas
- 		    [{- Nothing given -}]
- 		    [ mkClassPred num_class [ty] | ty <- tau_tys ]	`thenTc_`
+    	-- Check that all the types are instances of Num
+    	-- We only care about whether it worked or not
+    tcSimplifyDefault [mkClassPred num_class [ty] | ty <- tau_tys]	`thenM_`
     
-    	returnTc tau_tys
-
+    returnM (Just tau_tys)
 
-tc_defaults decls@(DefaultDecl _ loc : _) =
-    tcAddSrcLoc loc $
+tcDefaults decls@(L locn (DefaultDecl _) : _) =
+    setSrcSpan locn $
     failWithTc (dupDefaultDeclErr decls)
 
 
+tc_default_ty hs_ty 
+ = tcHsSigType DefaultDeclCtxt hs_ty		`thenM` \ ty ->
+   checkTc (isTauTy ty) (polyDefErr hs_ty)	`thenM_`
+   returnM ty
+
 defaultDeclCtxt =  ptext SLIT("when checking that each type in a default declaration")
 		    $$ ptext SLIT("is an instance of class Num")
 
 
-dupDefaultDeclErr (DefaultDecl _ locn1 : dup_things)
+dupDefaultDeclErr (L _ (DefaultDecl _) : dup_things)
   = hang (ptext SLIT("Multiple default declarations"))
       4  (vcat (map pp dup_things))
   where
-    pp (DefaultDecl _ locn) = ptext SLIT("here was another default declaration") <+> ppr locn
+    pp (L locn (DefaultDecl _)) = ptext SLIT("here was another default declaration") <+> ppr locn
+
+polyDefErr ty 
+  = hang (ptext SLIT("Illegal polymorphic type in default declaration") <> colon) 4 (ppr ty) 
 \end{code}